The present invention relates to material for cigarettes and a preparation method thereof, more particularly, to expanded stem fillers and a method for preparing the same, with the expanded stem fillers having modest and plain features, low content of flavor components, a uniform brown color and uniform expansion volume.
Tobacco stems, accounting for around 20% of weight of tobacco leafs, have chemical components basically same as leafs, but less contents of chemical components than leafs. Stem shreds converted from stems have low filling power, insufficient aroma, high irritation, low strength and strong wood taste. Researches and practices show that the above mentioned defects can be resolved through stem expansion, which means that expanded stems can be added into cigarette products in a large proportion, for enriching cigarette varieties and improving cigarette output.
As of yet, a lot of researches have been done on tobacco stem expansion by domestic and overseas enterprise research institutes.
Chinese patent CN 1759768A discloses a method for preparing reconstituted tobacco by a paper making process. This method utilizes low tier raw tobacco to manufacture reconstituted tobacco by using the paper making process. Because of the use of low tier raw tobacco, the final product has relatively strong irritation, offensive taste and wood taste.
Chinese patent CN 1748586A discloses a method and device for processing expanded stems. This method utilizes high-temperature steam and venturi mechanism for stem expansion and then cuts stems into shreds, and finally the expanded stems with relatively higher filling power are obtained. This method is of high cost, since the processing and equipment are complicated and the operational condition is severe. During the rapid pressurizing process with high-temperature and high-pressure steam, lattice of stem cells and stem epidermis are destroyed, which degrades stems.
Chinese Patent CN 1698481A and CN 1518906A disclose a method of preparing expansion stems and a method of preparing shreds. This method utilizes microwave for expansion after heating solid medium is mixed with stems. Even though this method is able to provide a higher ratio of expanded stems to total feeding stems, the solid medium heating system and the device for separating stems from medium are complicated and costly, and furthermore stems are contaminated, and environmental pollution is produced.
Chinese patent CN 101214086A discloses a method and equipment for pre-treating stems. The method utilizes heating air medium to pre-heat stems and then utilizes microwave for expansion to acquire expanded stems. When the heating air medium and stems are mixed and then fed into a microwave expansion chamber, the heating air medium temperature and the pre-heated stem temperature are dropped to a certain degree. During the microwave expansion process, the surface temperature of stems is low, which leads to a low ratio of expanded stems to the total feeding stems. If it is intended that temperature of the heating air medium and the stem surface is ensured during the expansion process, the temperature of the heating air medium is needed to be raised during the pre-heating phase, but the over-heated air will scorch the stem surface during the pre-heating phase, which might lead to spark phenomenon during the microwave process.
Chinese patent CN 1973699A discloses a method and device for using saturated or super-heated steam to continuously perform stem expansion. This method utilizes high-temperature steam for stem expansion. But because energy provided by steam is not enough, and furthermore the heating process is achieved by the way of heat transfer and the heat is transferred from outside to inside, therefore the ratio of expanded stems to the total feeding stems is not high and the color change of the stem surface is tremendous.
The above mentioned method as well as expanded stems or shreds prepared by the method are with some deficiencies: negative tastes like green gas and wood taste are found when the prepared stems are combusted, which impacts flavor and raw taste of cigarettes when introduced in cigarette blend; there is no uniform standard for final products, and the standard is defined by individual cigarette manufacturer; final product qualities (organ sensory, appearance) vary a lot, if the final products are produced from stems of different origins, different qualities and different batches. Because of deficiencies stated above, products of expanded stems are not put in place for being a commercial product traded on the market, which restrains large-scale application of stems. Market shows urgent demand for stem filler for cigarettes with modest, plain taste when combusted, low content of flavor components, uniform color and consistent expansion volume.